Calculating Transver BM of a catamaran

[Grimorum]

Hi All,

I am a beginner in studying naval arch.

Encountered a problem as follow and I cant seem to solve it.

Each of the two hulls of a catamaran has the following dimensions

Ord. No. 1 2 3 4 5 5.5 6
1/2 Ord(CM) 0 4 6.2 7.2 6.4 4.9 0

Length of each hull = 18m
Displacement each hull = 5.3meter cube
Ordinates are spaced evenly.

the hull center lines are 6m apart.

What is the transver BM of the boat?

I convert all dimensions to meter, then using Simpson first rule to calculate the y cube. Then using the formula: (1/3)integrate y cube dx and with the excel sheet, using this transverse second moment of area and divide it by the volume of displacement.

The answer I get is very far from the answer of 3.12m.

Hope someone can enlighten me in this question and best would be list out your steps.

 

[RAraujo]

Are you taking into consideration that you have 2 hulls and also the added transfer second moment of area due to the fact that each hull is 3m apart from CL?

 

[Grimorum]

RAraujo, very much appreciated, you just rang a bell in my head with that transfer second moment of area with the parallel axis theorem. totally forgotten about that. Got the answer now.

 

[TANSL]

If BM means "Bending Moment", you should get a result in kg.m.

 

[Grimorum]

BM in my case is the Center of buoyancy to the metacenter.

 

[TANSL]

Oops, sorry for my stupid mistake. I should have read your post more carefully.